The present invention relates to a terminal device used in a community antenna television (CATV) system.
Each terminal device has an identification address. In a two-way transmission CATV system, a data command signal is transmitted from a center to terminal devices connected to respective television receivers of subscribers by polling. The polling is a method of calling the terminals in sequence from a center to allow each in turn to transmit information data on hand.
The center sends a command signal including an address data and a command data to every terminal and receives a response signal including response data such as data for imposing a license fee from every addressed terminal in sequence. The terminal sends the data by a proper method, for example by a frequency shift keying (FSK) signal. In this way, the channel which the subscriber watches is monitored, thereby enabling to supervise pay per view (PPV) system of television programs. If the terminal device is provided with a special function module for two-way data transmission, programs wherein the subscriber can participate, such as opinion polls and shopping by television, become possible.
The terminal device is lent to the subscriber and withdrawn therefrom when the contract is cancelled. The data on the license of the withdrawn terminal device is erased by the center. The withdrawn terminal device is further lent to a new subscriber. When the terminal device is installed in the subscriber's house, the function of the device, the receiving condition of the FSK signal, the erasure of the data on the license fee for the old subscriber, and other data are confirmed. The function must be known for various purposes such as setting, and repairing the device. The FSK signal must be exactly received by the terminal device for performing the polling.
These data are known by the version of a microcomputer mounted in the terminal device and/or the appearance of the device. However, there are many versions in the microcomputer, and in the circuit modules thereof. In addition, the terminal device may be remodeled so as to provide additional functions to meet the requirement of the new subscriber. Therefore it is impossible to confirm the type and the function of the terminal device just by checking the labels on the outer cover or the appearance thereof. Therefore, the terminal device has heretofore been disassembled so that serviceman may confirm data on the identification, function, license fee and others of the terminal.
However, since the terminal device is usually assembled by special screws and rivets to prevent poaching and for other security reasons, the disassemble operation is extremely complicated, particularly in the case where the microcomputer is disposed in an inner portion of the terminal device.